Any idea why my baby cries every time he sees a certain playgroup worker?

From the very first visit to this play group my baby has screamed at the sight of this lady who works there and I feel so bad. She's not overly loud or too much either. But as soon as my baby sees her and she says hello he starts screaming, and I mean SCREAMING, tears streaming down his cheeks, properly huffing and hicupping and struggling to catch his breath. He isn't like this with anyone else, even strangers. And he's seen this woman countless times. Once he's in and settled at playgroup she can come up to him, hand him toys, blow bubbles for him etc, and he won't cry, and has even cracked a couple of smiles for her. But without fail, every time we walk in initially he absolutely loses it. But I'm too polite to say "please just don't greet us at the door" 🤣 Does anyone know why he's reacting like that though? I've never left his side at playgroup, she's never held him or been near him without me. I don't understand it 🥲